Many different differential interface ports with a positive and a negative data line are known. In particular, in the field of computers and peripheral devices connected to computers, the so-called Universal Serial Bus (USB) has become very widespread. In addition to the USB protocol, however, there also exist other differential interfaces for connecting electronic devices and components.
USB and technically similar interfaces support so-called “hot plugging,” that is, the connection and disconnection of peripheral devices to a host component while the host component and/or the peripheral device are running. Simultaneously, these interfaces support a plurality of different device types, such as, for example, mice and keyboards, memory sticks, external hard drives, and so on.
However, especially for the connection of external mass storage media to a running computer system, there is the risk that the security of a host system will be endangered.
For example, by connecting USB memory sticks, viruses or other malware could be transferred onto the host computer system. In addition, the theft of relatively large quantities of data is also very easy.
In order to counter these problems and similar problems, monitoring and filtering mechanisms are known that exclude the connection of certain device types to a computer system. For example, U.S. Pat. No. 7,043,587 B2 discloses a method and a system for controlling the addition of USB devices to a host computer system by means of a hardware hot-plug detector circuit that monitors USB ports. Here, when a new USB device is connected, a signal is transmitted in the form of a system management interrupt to an SMI handler in the BIOS of the computer system that then queries the device type.
Although the known solution features numerous advantages with respect to the security of the system, it also has several disadvantages. In particular, the monitoring function is implemented at least partially in software and thus is itself susceptible to hacker attacks. In addition, the protective mechanism engages only when a new device is connected and is based on the device class transmitted by the connected device. Thus, a connection of an unauthorized component cannot be prevented in every situation.